We need to be sure the command’s output, find in this case, issues only one filename per line. Note when we do read file, we read one line at a time from the standard input and store it in the variable file. Let’s try it using the same folder from the previous section: $ find files_to_check/ -type f | while read file doĪnd we get the right output: Testing files_to_check/with spaces.md5: From Wikipedia: The tilde symbol is used to prefix hidden temporary files that are created when a. We feed the filenames to the while loop using redirections. If youve always wondered what these files are, read on. In that case, an alternative approach will be iterating over the filenames with the read command inside a while loop. So, we can’t always use the method described in the previous section. Sometimes, we have a loop that can’t be easily separated, and also, we can’t get any arbitrary list of files with find. Now, let’s run check_file.sh with each file as the first parameter using find -exec: Now, let’s move the loop content to a file named check_file.sh: $ cat check_file.sh Testing files_to_check/without_spaces.sha256: Md5sum: spaces.md5: No such file or directory We can see that the for loop fails with the file named “ with spaces.md5“: Testing files_to_check/with: Let’s suppose we have a directory files_to_check/, and we have two files named “ with spaces.md5” and “ without_spaces.sha256” in it. Type the following command: cd / tmp / > -foo.txt > -bar.txt List files starting with a dash Try to list them, enter: ls -l. Let’s start with a for loop that iterates over the result of find: $ for file in $(find files_to_check/ -type f) do My second best one is search content similar to -something.First, let’s see how we can transform a loop that doesn’t work with spaces to the find -exec method. There are a few more situations where '-' could give you grief. Tar zcf -exclude=tmp/* /some/remote/volume/backup.tg my_data_folder/ In case you haven't noticed, now exclude option includes = sign. Then, in the version below, you can delete it and run the well-formatted tar command. The latest BASH version gives you a tip - don't use a relative path use the absolute one. Therefore, command treats - as an argument start character.įortunately, it has a straightforward fix. Rm '-exclude' That is not going to happen. None of the commands below would work because rm interprets it as an argument and fails to parse it. To find a file by name with the find command, you would use the following syntax: find -name ' query ' This will be case sensitive, meaning a search for query is different from a search for Query. The fun begins when you try to delete this file. It happens because the Linux kernel allows almost any character in the file and folder names, but not all commands concur. You may expect a new backup on some network device, but you create an archive ' -exclude' on your local filesystem. Let's take a look at the command below: tar zcf -exclude tmp/* /some/remote/volume/backup.tgz my_data_folder/ The Booby Trap commandĪt first glance, the command looks legit, except it does not. It adds to neverending fun because command-line warriors should memorize all kid of argument notations and formats for a score of the most common tools. System layer, user layer, core commands with the neanderthal accessory lines, modern commands, and all kinds of scripts. If you manage to find KSH or CSH nowadays, you have my respect.Īll *nix systems are similar to ogres and onions - all have layers. The commands below were tested on Red Hat Linux systems with Bash v4.x.
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